This invention relates to solid waste comminuting apparatus, and more particularly, to a comminutor in which solid waste material is sheared, shredded, and crushed while borne by a liquid such as water by the opposing forces of counter-rotation of peripheral overlapping interacting stacks of shredding elements.
A highly successful commercial solid waste comminutor is set forth in U.S. Pat. No. 4,046,324, to which the present invention has specific application. In general, comminution or the reduction of particle sized solid waste material to minute or fine particles is performed by shearing, shredding and crushing of waste material. Such comminution is performed by feeding solid waste material into the interface of counter-rotating innermeshed cutting elements. Such cutting elements may be of disk form or otherwise having radially projecting cutting teeth which overlap each other during rotation and with the cutting disks being spaced from each other within the given stack by smaller diameter spacers all fixed to respective shafts which extend parallel to each other and which are driven in counter-rotation. Shearing action occurs when the particles of waste material are clipped or cut by "scissors" action between the cutting elements on one shaft and those on the other shaft due to the overlap of root diameters of the cutting teeth carried thereby. Solid particles are sheared by the opposing forces of counter-rotation of the cutting teeth on the different stacks of cutting elements. The particles are also shredded by tearing action of the leading edge of a cutting tooth against solid material trapped between that cutting element and the opposite stack. The movement of the cutting element tooth passing by and through the trapped solid material also serves to crush the waste material.
Preferably, comminution is performed by feeding the solid material through the counter-rotating stacks of cutting elements while entrained in a liquid. Such entrainment not only conveniently achieves transport of the solid material to and through the comminutor, but additionally comminution is thereby aided by the process of maceration. Maceration is the softening and wearing effect of a liquid medium on a solid particle entrained within the liquid.
In U.S. Pat. No. 4,046,324 the stack of rotary disks form cutting elements with each disk spaced from the succeeding disk in the same stack by a smaller diameter spacer disk on the common shaft. Further, the cutting disks are peripherally overlapped at least to the extent of the root diameters of the cutting element teeth radially projecting from the disk proper. Shredding of solid waste material occurs within a comminution chamber defined by a rectangular cross-section casing, through which the axes of the paired shafts bearing the interacting stacks of shredding members or cutters extend.
Referring to FIG. 1 of the drawings, there is disclosed such a comminutor as depicted in U.S. Pat. No. 4,046,324. The comminutor, indicated generally at 10, is particularly useful in comminuting solid waste material borne by a liquid flowing through the interior of a casing indicated generally at 12. The casing forms a comminution chamber 14. The casing 12 is shown in vertical section to illustrate the components of the comminutor and the manner in which they achieve shredding of the solid waste. Purposely, this figure does not show the inlet port or outlet port which are on opposite sidewalls (not shown), into and out of the plane of the paper bearing FIG. 1.
The vertically upright, rectangular, cross sectional casing 12 includes a cast metal base 16 supported by a rectangular plate or cover 18 and bearing, in vertically upright position, a pair of side rails indicated generally at 20. Side rails 20 are connected at their bottoms by screws 22 to an upwardly projecting mounting plate 16a of base 16. At the top of casing 12, there is provided a mirror image cast metal casing head or upper frame member 24 of rectangular horizontal cross-section and which terminates, at it's bottom end, in a second mounting plate 24a. In similar fashion, further screws 22 project through the top of the side rails and are threaded within tapped holes (not shown) of head mounting plate 24a.
In FIG. 1, the vertical side walls of casing 12 are purposely not shown to permit viewing the interior of the casing, however, the casing includes opposed, vertical side walls. For a better understanding and appreciation of the nature in which the casing 12 is completed by such side walls, reference may be had to FIG. 2 of U.S. Pat. No. 4,046,324. One of the opposed side walls carries an inlet port which may be defined by a flange ring carrying a conventional pattern of bolt holes. The opposite side wall includes an outlet port which may likewise be defined by a flange ring through which are drilled bolt holes in a similar common pattern. This permits the comminutor to be mounted within a convention sewage or disposal conduit and the appropriate flange connections use the bolt holes to effect coupling to the sewage or disposal conduit section at opposite sides of the comminutor 10.
As clearly seen in FIG. 1, first and second shredding stacks at 26 and 28 are mounted in mutual, parallel alignment for counter-rotation on drive shaft 30 and idler or driven shaft 32, respectively. Shaft 30 is supported by an upper bearing assembly 34 within head 24 and by a lower bearing assembly 36 within base 16 respective. Shaft 32 is similarly supported for rotation about its axis and parallel to the axis of the drive shaft 30 by upper bearing assembly 38 and lower bearing assembly 40. respectively. In similar fashion to U.S. Pat. No. 4,046,324, the stacks 26, 28 may be compressed between opposing bearing plates (not shown) by nuts 41 on shafts 30, 32 backed by washers 43. The drive shaft 30 includes a drive gear 42 which is in mesh with a similar size driven gear 44 fixed to the upper end of the driven shaft 32. Rotation of the drive shaft 30 effects counter-rotation of shafts 30 and 32 about parallel axes. Drive is effected by an electrical motor indicated generally at 46 powered from an electrical source (not shown) through control box 48. A motor shaft (not shown) of the drive motor 46 is coupled mechanically to drive shaft 30 through a gear reduction unit indicated generally at 50 for driving the comminutor drive shaft 30 at an appropriate RPM suitable to the comminuting of particular solid waste material to which the unit has application.
As previously described, each of the stacks 26, 28 is formed of a number of laminar cutting elements which are preferably of disk form. The cutting elements are directly mounted on the shafts 30, 32. The shafts may be of hexagonal cross sectional configuration with the cutting elements having corresponding holes or openings through the center of the same. The cutting elements 52, 54 are positioned between and separated in the axial direction along respective shafts 30, 32 by laminar spacers 56, 58, respectively, in the form of circular disks of reduced diameter with respect to the cutting elements 52, 54. Preferably the thickness of the cutting elements 52, 54 and the spacers 56, 58 are the same so that the laminar spacers of one stack are coplanar with cutting elements of the other stack. Thus, a cutting element from one stack and a spacer from the other stack form together a pair of interacting shredding members. While cutting teeth (not shown) integral with the cutting elements and projecting radially thereof overlap each other to the extent of their root diameters, there is always a slight gap between the outer periphery of the cutting element teeth of one stack and the periphery of the opposed laminar spacer of the other stack. Insofar as the present invention is concerned, the make up, assembly, and the nature of the drive imparted to the cutting elements herein is identical to that of U.S. Pat. No. 4,046,324.
In that respect, casing 12 is of rectangular parallelepiped form. Side rails 20 are of cast metal construction as are the base 16 and head 24. The side rails are also of rectangular plan configuration with the top and bottom of the side rails being mounted directly to mounting plates 16a and 24a of the base and upper frame 24, respectively. While the sectional view of FIG. 1 shows the side rails as having their interior surfaces 20a which face each other flat, the side rails of the prior art apparatus may take the form shown in U.S. Pat. No. 4,046,324 and include along opposite ends thereof, triangular shaped projections functioning as deflectors for deflecting the flow of solids into the leading edges of the radial cutting teeth projecting outwardly of the periphery of the disk like cutting elements forming the stacks 26, 28 along with the interposed spacers. The comminutor 10 of FIG. 1 as per U.S. Pat. No. 4,046,324 performs quite adequately and constitutes a marked improvement within the art and while it permits the stacks to rotate in either direction due to the presence of cutting edges on both sides of the cutting teeth, thereby providing increased flexibility and a greater length of cutting surface within an increase in the dimensions of the comminutor. However, little attention has been given to the possible adverse action, by the components making up the casing as well as the stacks, to the through put or flow rate of the fluid carrying the solid particles into the comminution chamber and removing of fine particles thereof from the chamber after shearing, shredding and crushing.